The European surgeon, Acipenser sturio, used to be found along the coasts and in many rivers in Western Europe.
Industrial development, arrangement and equipping rivers and estuaries, then in the 20th century, intensification of fishing, particularly for making caviar, had led to their practical disappearance.
Other aggravating factors include deterioration of water quality, gravel extraction destroying the spawning grounds, creating obstacles to hinder the movements of this great migratory fish that reproduces in the river and grows in the estuary and then at sea. In the 1980s, there was just one single worldwide population of European sturgeon, originating from the Gironde-Garonne-Dordogne basin.
Despite being protected by regulations since 1982 in France, then in 1998 on a European scale, this community has continued to wane and was almost wiped out completely in the 2000s.
Long, drawn out research
The first research by Irstea to study the condition of this population began in 1975. Aware that protecting the species would not be enough to curb its rapid decline, having seen the rarity of its natural reproduction, scientists studied possibilities of helping nature by running assisted reproduction working with wild spawners, raising alevins up to a stage when they had a good chance of survival. However, the rarity of the spawner returns only gave them 3 chances at reproduction in 15 years. Only the last opportunity in 1995 allowed them to successfully breed the alevins. This rarefying of the species showed that the only chance of restoring the population was to control setting up a stock of sturgeons brought to maturity, to avoid dependency on the last chances of capture in the natural environment.
The first production of alevins by assisted reproduction in 1995, within the framework of a LIFE programme, using two male and female spawners captured accidentally by fishermen, plus the capture of a fraction of juvenile fish from the last reproduction known in the natural environment in 1994, was successful and so this precious stock could be set up. From the 23,000 obtained in 1995, around 9000 larvae could be obtained and released into the Garonne and Dordogne, and just a thousand were kept at St Seurin sur l’Isle (main stock) and in Berlin (experimental safety stock) to contribute to the stock of future spawners. However, we will have to wait another twelve to fifteen years for them to attain their first sexual maturity.
With the help of a second LIFE programme, then within the framework of CPER Aquitaine (state-region project contract), Irstea researchers completed the first results for this conservation strategy in 2007. They obtained the first artificial reproduction using specimens raised from a very young age in their experimentation station at Saint Seurin sur l’Isle. Out of the 11,000 larvae obtained, 7,500 were released back into the Garonne and the Dordogne three months later and a fraction were kept at St Seurin and in Berlin to renew the stock of spawners when the time comes or were released 8 months later when they were large enough to be marked and monitored using transmitters.
2008 confirmed this first success. The first reproduction test, performed by Irstea on 29th May 2008 on a group of 7 males and 7 females led to hatching 13,000 larvae. A second test followed on 18th June with a different batch of 7 males and 6 females, leading to hatching 80,000 larvae. Small batches of eggs were even fertilised successfully using sperm that had been frozen, thereby validating the possibility of using this technique.
As the result of two new successful attempts at artificial reproduction, almost 10 times more larvae were obtained than in 2007, hatching 86,000 alevins in 3 months, in addition to the fraction kept to renew the stock of spawners. This result has renewed hopes of repopulating the Gironde basin and has led to the first experimental hatching on the Elbe. Beyond the size of the stock obtained, this result represents important scientific progress. Sturgeons from 2008 reproduction have proved to be more resistant to handling than the 2007 spawners and the survival rate for larvae improved significantly.
In 2009, new artificial reproduction has allowed hatching and stocking to continue with 45,000 alevins released into the Dordogne and Garonne. This third success was able to rebalance the acclimatised stock, by releasing a fraction of alevins from 2007 kept in the station: these 2 year old juveniles released into the estuary will stay there and then move towards the Atlantic Ocean, the English Channel and the North Sea to reach their adult stage. They should return in around twelve years to reproduce. Individually marked, these sturgeons are going to be monitored closely by scientists.
And in 2010…
Since spring 2010, thanks to the joint efforts of the National Fisheries Committee and Irstea, the number of accidental captures declared by amateur and professional fishermen in the Gironde has slightly increased. These captures provide scientists with information on the size and the location of the fish (further downstream in the Gironde for the stock from 2007 and 2009), particularly when they fish with a drift net (lamprey and shade-fish). The fish released from the nets measure 40 to 75 cm and seem to be healthy overall and well developed.
Systematic sampling and individual marking campaigns led by Irstea with l’Esturial in Gironde have begun and must intensify in the months and years to come to verify the efficacy of hatching and appreciate the population numbers reconstituted in this way.
A great scientific step has been taken
Successive reproduction successes have helped reproduction of older spawners, favouring genetic diversity of the population and the acclimatised stock. Furthermore, cryopreservation techniques could be applied to increase the possibilities of crossing and guarantee future reproductions.
However, important progress remains to be made in terms of feeding spawners, selection and choice of intervention periods, reproduction and larva raising techniques, before the transfer of future spawner management and the production of alevins for large scale repopulation of specialised structures (new structure to be set up or private fish farms).
The success of this programme to "save" a species that had practically disappeared from rivers and Atlantic coasts after having been so common there, by using conservation methods and aquaculture production, means that we can hold off the loss of the greatest migratory fish in Western Europe. It is not enough to avoid the threats that have brought about this situation, although we do have to hammer away them, to restore this species on the major rivers and the coasts that it used to frequent.
All the actions undertaken can only be useful if awareness is raised among fishermen in terms of protecting this endangered species and by conserving and restoring quality environments, to wait for the return of the wild spawners in 15 years' time.
The success of a long scientific partnership
These results, the fruit of 30 years of research on the species led by Irstea and its scientific partners, can contribute to operational implementation of the international and national plan to restore the European sturgeon, by applying obligations arising from the Berne and Bohn conventions and by classifying this species as a priority for the Habitats Directive.
The programme to save this species, coordinated by the Aquitaine Regional Board for the Environment, Development and Accommodation (DREAL), brings together WWF France, public establishments for EPIDOR basins (Dordogne basin), SMEAG (Garonne basin) and SMIDDEST (Gironde estuary), the CNPMEM (National Committee for Sea Fishing and Marine Breeding) and benefits from the support of FEDER Aquitaine, the Ministry for the Environment, the Aquitaine and Poitou Charente regions, the departments of Charente Maritime and Gironde and the Adour Garonne Water Agency.